Pressure relief for fluid pumps



April 17, 1956 J. B. PARSONS 2,741,985

PRESSURE RELIEF FOR FLUID PUMPS Filed Jan. 14, 1953 7 I 1 l7 321 i I 215 i l 1 I 22 I l l /J J 9 2 I i 1 l1 H J f I I w 1 Mb am I d L 1% H 12 I H A 13 INVENTOR. JOHN B PARSONS BY W qlxuzm LL62.

AT TY.

Un ed States Patent 'Thisinvention" relates to motor and pump units, but

particularly to those which include an electric motor, a

hydraulic pump and a reservoir for liquid handled by the pump.

An object is to produce a new and improved pressure relief device for a hydraulic pump which will not chatter;

; can beinexpensively produced and installed; can be conveniently. adjusted for the maximum'pressure desired; and is'sturdy and reliable in operation.

Another object is to produce a pressure relief valve in- ;stallation-. in a motor and pump assembly wherein the hydraulic. pump is arranged within the liquid reservoir and the. said installation is likewise arranged therein with :provision for regulating the relief pressure from the outside.

Furtherobjects and advantages ofthe invention will ;the reinafter-;appear, and for purposesof illustration but not of limitation, an embodiment of the invention is shown on the accompanying drawings, in which:

Figure l is a side elevation of a motor and pump assembly, part of the reservoir being broken away to show the hydraulic pump and associated parts;

Figure 2 is a fragmentary side elevation of the assembly with a portion of the reservoir broken away to show the interior thereof, the hydraulic pump being shown in vertical section to illustrate the spring-tensioned ball valves; and

Figure 3 is a transverse sectional view on the line 3-3 of Figure 1.

The illustrated embodiment of the invention comprises an electric motor unit 10, the upper end of which is closed by an end plate on which is mounted a hydraulic pump 11 of the rotary gear type. The housing of the pump is in two parts, 12 and 13, secured together by cap screws 14. The screws 14 extend into the end plate of a reversibleelectiic motor 10, and holds the pump in the desired position within an upright liquid reservoir 15 which is of inverted cup shape. The lower end of the reservoir abuts against the motor end plate with an ap-,

propriate liquid-tight seal between the mouth of the reservoir and the end plate. Disposed within the reservoir 15 is a pair of vertical tubes 16 arranged in parallel relation, each having a screw-threaded lower end 18 for engagement with the upper pump housing section 12, these tubes being aligned with the ports of the pump serving as inlet and outlet of same. It will be observed that the tubes 16 extend through the top wall of the cylindrical reservoir 15 and suitable fittings 19 secure and seal the tubes in place and also hold the reservoir in place. Leading from the fittings are tubes 20 for conducting liquid under pressure to and from the work. A screw filler plug 21 is disposed in the top wall of the cylinder 15 and is arranged at one side to enable a screw driver S to be inserted therethrough for a purpose hereinafter to be described. I

Within the pump housing is a pair of normally open springtensioned ball check valves 22 which control the 2,741,985 Patented Apr. 17, 1 956 passages leading from the reservoir to the pump motor respectively. It will be understood thathydraulic pressure generated by the pump, depending upon the direction of rotation of the motor, is sufficient to unseat one or the other of the spring-tensioned valves 22, and by thus seating a particular ball check, liquid will be forced into one or the other of the vertical tubes 16 and 17, the other of these tubes serving as a return conduit from the work to enable such liquid then to return to the reservoir 15. It will be understood that the reservoir 15 is filled with liquid, such as oil, and that the pump 11 is disposed within such liquid, thereby enabling the use of a less expensivehousing since the problems of liquid seal are not of great concern. Detail description and illustration of the pump is not considered necessary here. Reference, however, is made to my application Serial No. 173,526, filed July .13, 1950, and entitled Motor and Pump Assembly" (now Patent 2,622,529 and dated December 23, .1952),

wherein afull and complete description of the. structure and operation of the pump are set forth.

The spring-tensioned ball check valves 22 are within chambers 23 in the upper housing part12, and leading from each of these chambers is a passage 24 which opens into the interior of the reservoir 15. It will be understood that thecheck valves 22 controlthe flow of liquid from the reservoir 15 to the respective chamber 24 and when pressure is built up to force one of these balls to its seat,

then the liquid will flow into the adjacent vertical tube instead of passing into the reservoir. On the other hand, :the otherball-being open, enables liquid from the reservoir or from theradjacent vertical tube to pass to the. low pressure side of the pump, as will be readily understood.

These passages 24 afford pressure relief passages and each is controlled by a ball valve 25. As shown, each ball valve 25 is considerably larger than the mouth of the associated passage 24 and does not seat well within the month. On the contrary, each valve 25 seats on the mouth of such passage in such manner that the greater portion of the ball is disposed outside of the mouth. Such arrangement is found to be of importance in obviating chattering of the bails when moved to and from seating position. Is is found empirically that providing a ball of considerably larger diameter than that of the passage with which it is associated, objectionable chattering and the noise incident thereto are obviated.

The ball relief valves 25 are normally held in seated position by a cross shaped spring device which has a flat elongate body 26 of spring metal, the ends of which are notched as indicated at 27, one end embracing a smooth shank 29, which provides an extension of one of the cap screws 14 and has a head 28. The other notched end of the spring body 26 embraces a threaded shank 30 which provides an integral extension of the other cap screw, as shown in Figure l, and screwed on to this extension is an internally threaded sleeve 31, the upper end of which is notched to receive a screw driver.

Integral with the body 26 is a pair of oppositely extending spring arms 32 arranged on the body somewhat closer to the screw-threaded shank 30. Each arm 32 inclines downwardly and outwardly from the body 26 and terminates in a flat portion parallel to the plane of the body 26. Each flat portion of the arms 32 engages the top of one of the ball valves 25, imposing a spring pressure thereagainst to hold the same in seated position. When the hydraulic pressure within one of the chambers 23 is sufficiently great to overcome the pressure exerted by the respective spring arm 32 upon the respective ball valve 25, the latter is lifted from its seat to enable the pressure to be relieved, excess oil passing into the reservoir. As soon as the pressure is relieved, then the ball 25 automatically returns to its seat.

The pressure exerted by the spring arms 32 may be controlled by adjustment of the sleeve 31. Thus by screwing the sleeve 31 downwardly to force the end of the body 26 downwardly, a greater pressure is imposed upon the balls 25 in a uniform manner, and by unscrewing the sleeve 31, the pressure on the balls 25 is reduced. The filler opening which is closed by the screw plug 21 is so arranged as to be directly above the sleeve 31 so that by removing the filler plug, 21, a screw driver S may be moving the filler plug and inserting a screw driver. Al-

though ordinarily it is regarded that ball valves are not suitable for this purpose, because of objectionable chattering when moved to and from their seats, however, by employing balls considerably larger than their seats, this objection is overcome. This is probably due to the fact that the ball has relatively short movement to become unseated and permit the passage of liquid than would be the case where the ball seated substantially within the passage which it controls. In any event, the result has been exceedingly satisfactory and the pressure relief is achieved noiselessly and efficiently.

It is to be understood that numerous changes in details of construction, arrangement and operation may be effected without departing from the spirit of the invention especially as defined in'the appended claim.

What I claim is:

A motor and pump assembly comprising a reversible electric motor, a cup-shaped sheet metal reservoir in end to end abutting relation to'said motor with the open end of the reservoir facing the motor, a pump 'unit arranged wholly within said reservoir and operatively connected to be driven by said motor, said pump unit including a housing having a pair of valve controlled passages communicating with the interior of the reservoir, ball pressure relief valves associated with said passages respectively for relieving excessive pressure within the housing leaf spring means for normally holding said relief valves seated comprising a cross-shaped leaf spring, means to anchor opposite ends of the body of the spring, the cross arms of the spring engaging the ball valves respectively, means accessible through the reservoir for adjusting the tension imposed by the spring, tube means extending from the pump through the reservoir with end portions projecting through openings in the closed end of the reservoir, and means engaging said projecting tube end portions for securing the reservoir to the motor.

References Cited in the file of this patent UNITED STATES PATENTS 1,173,703 Benkert Feb. 29, 1916 1,352,123 Green Sept. 7, 1920 1,416,695 Dennedy May 23, 1922 1,416,696 Dennedy May 23, 1922 1,780,121 Dunning Oct. 28, 1930 2,032,885 Murphy Mar. 3, 1936 2,202,912 Johnson June 4, 1940 2,246,610 Wagner June 24, 1941 2,268,695 Carlson Jan. 6, 1942 2,393,406 Parsons Jan. 22, 1946 2,405,466 Tabb Aug. 6, 1946 

